1. Field of the Invention
This invention relates to a liquid crystal display, and more particularly to a driving method and apparatus for a liquid crystal display including red, green, blue and white color filters.
2. Description of the Related Art
Generally, a liquid crystal display (LCD) controls light transmittance of liquid crystal cells using an electric field to thereby display a picture. To this end, the LCD includes a liquid crystal display panel having a pixel matrix, and a driving circuit for driving the liquid crystal display panel. The driving circuit drives the pixel matrix such that picture information is displayed on a display panel.
FIG. 1 schematically shows a related art LCD. Referring to FIG. 1, the related art LCD includes a liquid crystal display panel 2, a data driver 4 for driving data lines DL1 to DLm of the liquid crystal display panel 2, a gate driver 6 for driving gate lines GL1 to GLn of the liquid crystal display panel 2, and a timing controller 8 for controlling a driving timing of the data and gate drivers 4 and 6. The timing controller 8 receives a dot clock DCLK, a horizontal synchronizing signal Hsync, a vertical synchronizing signal Vsync, a data enable signal DE and data. The timing controller 8 re-arranges the received data and applies the rearranged data to the data driver 4. Further, the timing controller 8 generates timing signals for controlling the timing of the data driver 4 and the gate driver 6 and control signals such as a polarity inversion signal.
The gate driver 6 sequentially applies a gate signal to the gate lines GL1 to GLn in response to a control signal from the timing controller 8. The data driver 4 converts R, G and B data from the timing controller 8 into analog data signals to thereby apply data signals for each one horizontal line to the data lines DL1 to DLm during each horizontal period when the gate signal is supplied to the gate lines GL1 to GLn.
The liquid crystal display panel 2 includes thin film transistors TFT and liquid crystal cells. The thin film transistors TFT are provided adjacent to crossings of an n number of gate lines GL1 to GLn and an m number of data lines DL1 to DLm. The liquid crystal cells are connected to the thin film transistors TFT and have a matrix structure.
Each thin film transistor TFT applies a data from one of the data lines DL1 to DLm to a liquid crystal cell in response to a gate signal from one of the gate lines GL1 to GLn. The liquid crystal cell comprises a common electrode and a pixel electrode. The pixel electrode is connected to the thin film transistor TFT. The common electrode is opposite the pixel electrode. A liquid crystal material is disposed between the common electrode and the pixel electrode. Thus, the liquid crystal cell can be equivalently expressed as a liquid crystal capacitor Clc. Such a liquid crystal cell is provided with a storage capacitor Cst connected to the pre-stage gate line in order to store a data voltage charged in the liquid crystal capacitor Clc until the next data voltage is charged therein.
FIG. 2 is a detailed perspective view of the liquid crystal display panel shown in FIG. 1. As shown in FIG. 2, the liquid crystal display panel 2 comprises a color filter array substrate 24 and a thin film transistor array substrate 26 joined to each other and having a liquid crystal 18 therebetween. The liquid crystal 18 rotates in response to an electric field applied thereto, thereby controlling a transmitted amount of an input light, through the thin film transistor array substrate 26, from a back light (not shown).
FIG. 3 depicts the color filter array shown in FIG. 1. The color filter array substrate includes a color filter array 14, a black matrix 12 and a common electrode 16 that are provided at the rear side of an upper substrate 11. As shown in FIG. 3, the color filter array 14 comprises red (R), green (G) and blue (B) color filters. Such red (R), green (G) and blue (B) color filters transmit light within a specific band of wavelengths to thereby display color images. The black matrix 12 is provided between the adjacent color filters R, G and B to absorb a light emitted from adjacent cells. In other words, the black matrix 12 absorbs light emitted from the adjacent cells to prevent contrast degradation.
The thin film transistor array substrate 26 shown in FIG. 2 includes a pixel electrode 20. The pixel electrode 20 is provided at the front side of a lower substrate 22 and is connected to the thin film transistor TFT provided adjacent to a crossing of a data line DL and a gate line GL. The pixel electrode 20 can be made of a transparent conductive material having a high light transmittance. Such a pixel electrode 20 generates a potential difference with respect to the common electrode 16 when a data signal is applied through the thin film transistor TFT, thereby rotating the liquid crystal 18 in a desired direction. Then, a desired light propagating through the liquid crystal 18 is emitted through the R, G and B color filters provided for each liquid crystal cell Clc, thereby displaying a desired picture.
FIG. 4 represents a driving process of the liquid crystal cell shown in FIG. 1. First, a data signal is applied to each liquid crystal cell Clc during one frame interval 1F. Then, the liquid crystal 18 of each liquid crystal cell Clc is rotated in response to the data signal. A light supplied by an external back light (for example, a cold cathode fluorescent lamp (CCFL)) is controlled by the liquid crystal cell Clc (i.e., in response to a rotation of the liquid crystal cell 18) and transmitted to the color filter array 14. Thereafter, a light supplied through the liquid crystal cell Clc is converted into colored light by the red (R), green (G) and blue (B) color filters, thereby displaying a desired color picture.
The related art LCD has the following drawbacks. The color filter array 14 includes only three initial color (R, G and B) filters, which limits the display of vivid colors. Also, the related art red (R), green (G) and blue (B) color filters have a transmittance less than 50%, which makes achieving high brightness difficult.